• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.6
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• pp.393-401
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• 2021

In this paper, we proposed a numerical model based on moment-curvature, to evaluate the resistance of reinforced concrete (RC) members subjected to blast loading. To consider the direct shear failure mode, we introduced a dimensionless spring element based on the empirical direct shear stress-slip relation. Based on the dynamic increase factor equations for materials, new dynamic increase factor equations were constructed in terms of the curvature rate for the section which could be directly applied to the moment-curvature relation. Additionally, equivalent bending stiffness was introduced in the plastic hinge region to consider the effect of bond-slip. To verify the validity of the proposed model, a comparative study was conducted against the experimental results, and the superiority of this numerical model was confirmed through comparison with the analytical results of the single-degree of freedom model. Pressure-impulse (P-I) diagrams were produced to evaluate the resistance of members against bending failure and direct shear failure, and additional parametric studies were conducted.

• Journal of the KSME
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• v.25 no.5
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• pp.413-418
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• 1985

직접 접촉식 교환장치(이하 직접 교환기라 함)에서 액체의 유통형태의 선택은 매우 다양하며 전달계수 역시 개별적인 상황이나 충전물의 종류에 따라서 달라지므로 일률적으로 제시되지 못 하고 있다. 많은 경우 실험을 통하여 열전달 또는 물질전달계수를 측정하게 되나 개수로, 자유 낙하액체막, 액체분류와 같이 이상화가 가능한 경우, 이러한 전달계수를 구하기 위하여 이론적 또는 반실험적인 해석을 수행하기도 한다. 수많은 관련 연구결과들은 층류유동에 관한 것과 난류유동의 경우로 구분되고(예상되듯이 대부분의 직접교환기의 유통영역은 난류쪽이다), 난류 유통의 해석은 다시 표면갱신이론(surface renewal model), 와류확산계수모델(eddy diffusivity model-macroscopic), 미분형와류모델(differential eddy diffusivity model)로 대별된다. 여기서는 수많은 교환기형태의 자료정리보다 상기와 같이 대별된 액체측 유동영역별로 전달현상해석의 방법을 간단히 정리하고자 한다.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.287-290
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• 2003

다모선 계통의 정확한 과도 안정도 직접해석을 위해 댐핑영향은 고려해야 할 중요한 요소 중의 하나이나 일반화가 어려워 최근까지 무시되어 왔다. 본 논문에서는 시스템을 나타내는 함수들의 적분 관계식들을 고려함으로써 다모선 계통에서의 댐핑영향을 반영한 에너지 함수를 유도하였으며 유도 과정에 있어 최근 다모선 계통에 보편적으로 적용되고 있는 관성중심(Center of Inertia :COI) 표현법으로 전개를 시도하였다. 유도된 에너지함수를 PEBS(Potential Energy Boundary Surface) 직접법에 적용하여 임계위치에너지를 산출하였으며, 임계고장제거시간을 계산함으로써 과도안정도직접해석법을 수행하였다. 제안된 에너지 함수를 WSCC 3기 9모선 샘플 시스템에 적용하여 댐핑이 고려된 에너지함수가 실제 계통을 보다 정확하게 표현하고 있음을 시뮬레이션을 통해 검증하였다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.1
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• pp.27-33
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• 2016

A numerical analysis on deck wetness is carried out for a large caisson directly wet-towed by tugs in irregular waves. A constant panel method is used for linear analysis in frequency domain and a statistical post-processing for the deck wetness is presented. Hydrodynamic coefficients obtained from the frequency domain computation are imported for time domain analysis which enables complete modeling for towing equipment, environment, etc. Both frequency and time domain computations over two sea states are performed and comparison is made. In the time domain analysis, towing systems of various arrangements of tugs are investigated from short-term prediction for the largest deck wetness and the number of occurrences of deck wetness.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.6
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• pp.1082-1091
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• 1989

본 논문에서는 응고계면을 기준으로 하여 액상역, 고상역 및 로울등을 각각 계산 가능한 영역으로 좌표변환하는 경계공정법을 사용하여 로울두께 방향의 온도분 포와 고상역과 액상역의 속도 분포를 고려한 2차원 응고해석을 하여 모델재료를 이용 한 실험결과와 비교 검토하여 이론해석의 타당성을 검정한다. 그리고 열전도율이 연 강보다 적어 박판제조가 어려운 재료인 스테인리스강을 용탕으로부터 직접 생산하기 위한 압연조건을 정량적으로 제시하며, 압연로울의 냉각특성을 밝힌다.

• Tunnel and Underground Space
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• v.12 no.1
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• pp.37-42
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• 2002

A back analysis algorithm was developed to determine the major parameters for tunnel design; the elastic modulus(E) and the ratio of horizontal to vertical stress(K). The algorithm is based on direct search method and was coded by FISH language of FLAC, a commercial finite difference program. Developed code was applied on some models to verify the validity and estimate the efficiency of the algorithm. Verification by theoretical solutions and published results of Gens' research, was successful.

• Journal of Korean Society of Steel Construction
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• v.25 no.5
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• pp.487-495
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• 2013

As the first step to suggest effective ways of using direct analysis method considering current situations of construction fields in Korea, analytical approach is used to verify direct analysis method which adapts initial imperfection limitation of Korean specification of building construction. The main analytical variables are size of frames, axial load ratio, axial load distribution, value of notional loads, location of notional loads, and applied method of notional loads. The results show that the use of initial imperfection limitation of Korean specification, L/700 is suitable, and the recommendable method to use direct analysis method is applied notional loads based on L/700 as minimum lateral load at each story, even if B2 is less than 1.5 and lateral loads exist.

• Journal of Korean Society of Steel Construction
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• v.22 no.1
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• pp.87-97
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• 2010

The purpose of this study was to evaluate the validity of the second-order analysis for asymmetric unbraced frame using the load amplification factor suggested by design codes. For this purpose, the first-order analysis with the B1 and B2 factors suggested by KBC 2005 and the direct analysis with the load amplification factors suggested by KBC 2009 were performed for five story - two bay and five story - four bay asymmetric unbraced steel frames. The results of the analyses were compared with the results of the second-order inelastic analysis to evaluate the validity of the suggested methods. The main parameters of the analysis were the shape of the frame, the axial load ratio of the column, the methods of analysis and the location of column. The research results show that the asymmetric shape of the frame deteriorates the validity of the factor B2 and the suggested methods. The range of error is increased in case of irregular or inclined column.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.11a
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• pp.20-20
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• 1997

고강도 알루미늄 대형 링롤재를 급냉할 때 발생하는 잔류응력을 2차원 및 3차원 유한 요소 해석하였고, 3단계 절단법에 의해 측정된 변형율과 ABAQUS의 요소제거 기능을 이용한 해석 값을 직접 비교하였다. 급냉후 잔류응력 해석결과는 2단과시효 후 측정값과 비슷한 경향을 보였으나 그 절대값의 차이가 크게 나타났다 이는 시편 링의 높이가 작아 실험 값이 부정확하였기 때문이며 링의 높이를 증가시켜 높이방향으로 균일한 응력분포를 갖도록 하면 그 차이가 감소될 것으로 판단된다. 잔류응력을 측정하는 3단계 절단 과정을 모사한 3차원 해석결과와 측정된 변형율을 직접 비교함으로써 실험과 해석의 정확성을 향상시킬 수 있도록 하였다. 이로부터 잔류응력이 존재하는 일반적인 알루미늄 구조물의 기계가공에 의한 변형을 정확히 예측할 수 있는 기반을 마련하였으며 구조해석 시 잔류응력의 영향을 고려할 수 있게 되었다.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.3
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• pp.62-71
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• 1995

In the numerical analysis of incompressible unsteady Navier-stokes equation, large time is required for solving the pressure Poisson equation of the elliptic type at each time step. In this paper, a numerical analysis by the direct method is carried out to solve the pressure Poisson equation and the computing time is analyzed as mesh size increases. The pressure Poisson equation can be transformed to the boundary value problem by the Green theorem. The computing time for the convolution type of the domain integral can be reduced by using F.F.T. and the computing time in the direct method depends entirely on obtaining the solution of the boundary value problem. The numerical analysis on the known solutions is carried out and compared for the verification of the direct method. And the numerical analysis on the body boundary and domain decomposition problem are carried out with the computing time less than O($n^{3}$) in the (n.n) mesh.